<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>子元素选择器</title>

    <style type="text/css">
        * {
            padding: 0;
            margin: 0;
        }

        ul {
            list-style: none;
        }

        .list li {
            width: 100px;
            height: 100px;
            background: #cccccc;
            float: left;
            margin: 5px;
        }

        .list li:first-child {
            background: #c00;
        }
    </style>
</head>
<body>
<ul class="list">
    <li>1</li>
    <li>2</li>
    <li>3</li>
    <li>4</li>
    <li>5</li>
    <li>6</li>
    <li>7</li>
    <li>8</li>
    <li>9</li>
    <li>10</li>
</ul>
</body>
</html>